On June 12, 2018, Nintendo announced that hugely popular battle-royale videogame Fortnite would be coming to the surging Nintendo Switch gaming console.

But there was a double bonus that day for Switch owners: The game was available for download immediately, and it was free.

That very same day, videogame streaming site Twitch.tv exploded with activity for Fortnite, as you can see in the graph below.

By looking at the number of viewers day by day and hour-by-hour since April 2018, the spike on June 13 is even more pronounced. A typical day's viewership for League of Legends spikes at an already impressive 500,000 viewers, but on June 13, that number exploded to almost three times that - 1.48 million concurrent viewers all watching people play Fortnite.

On any given day, Fortnite is already one of the most-popular games that people stream and watch on Twitch. We recently reported that it was the most-streamed game on Twitch for all games, beating out videogame stalwart League of Legends.

Twitch.tv, owned by Amazon, is seeing massive growth, with the number of games being streamed up 30% in just the past six months.